Sidebar: Other Ways to See, October 2003

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other ways to see

The Artificial Retina Project isn't the only player in the race to restore vision. Two other teams are working on different approaches to helping patients suffering from age-related macular degeneration and retinitis pigmentosa.

Optobionics of Napervile, Ill., is implanting an artificial silicone retina that is placed behind the eye, in a subretinal approach. In contrast, the retinal prosthesis being developed for the Artificial Retina Project is implanted on the surface of the retina, in an epiretinal approach.

Optobionics' microchip has 5,000 photodiodes, or solar cells, that are intended to stimulate the remaining healthy retinal cells, and use them to process images. The chip is designed to function with the power provided by light entering the eye, and does not require connecting wires, batteries, or other ancillary devices. According to the company, six patients have been implanted with the chip in clinical trials, and they report having the ability to perceive light and decipher shapes.

William H. Dobelle is trying an even more unusual approach, a brain implant, that he says can restore vision to people suffering from all types of blindness. With Dobelle's procedure, a 16-electrode plate is implanted on a patient's visual cortex. The patient wears a video camera mounted on special glasses, which connects to a computer worn in a waist pack. The computer interprets and simplifies the video images and transmits them to the implanted electrodes. The electrodes are then electrically stimulated to create some semblance of light.

When stimulated, each electrode produces one to four closely spaced phosphenes.

Patients are reportedly able to see the outlines of shapes and to be able to drive a car, according to the Dobelle Institute in Lisbon, Portugal.

Dobelle claims to have implanted the device in eight patients suffering from blindness caused by traumatic injury and infection, who did not necessarily have intact retinas. The device is commercially available in Europe, but has not been approved for trials or use in the United States by the Food and Drug Administration.

Researchers in the Artificial Retina Project are skeptical of both rival approaches.

Mark Humayun, a professor of opthalmology at the Doheny Eye Institute of the University of Southern California, said of the subretinal approach: "The idea is that the presence of this chip will rescue photoreceptor cells before they die. But tests have shown that implanting a dummy chip will have the same effect on vision. Even an operation that does nothing but open up the eye will have a restorative effect for about a year."
Dobelle's method, critics say, yields benefits, but also entails serious risk.

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